MIPS: Lemote 2F: Add basic CS5536 VSM support

Lemote Loongson 2F family machines use CS5536 as their south bridge and need
these lowlevel interfaces to access the devices on CS5536.

Virtualize the legacy devices on CS5536 as PCI devices.  This way users can
access the CS5536 PCI config space directly as a normal multi-function
PCI 2.2 device.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
Cc: zhangfx@lemote.com
Cc: yanh@lemote.com 
Cc: huhb@lemote.com
Cc: Nicholas Mc Guire <hofrat@hofr.at>
Cc: Arnaud Patard <apatard@mandriva.com>
Cc: loongson-dev@googlegroups.com
Cc: linux-mips@linux-mips.org
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>